lOi) MARINE BIOLOGY OF THE SUDANESE RED SEA. 



I. The specimens differ superficially from S. hartmeyeri : 



(1) in being much more ramified and crowded colonies; 



(2) in the absence of any trace of foliate lower branches ; 



(3) in their colour-scheme, which is due to the thick covering of 



crimson spicules. As to the colour of the living specimen. 

 Mr. Crossland notes that it appeared jet-black when seen 

 through a fathom or two of clear water, but when brought up 

 it showed a splendid d:irk crimson, shading into pink on 

 the stem. 

 They differ more intimately in the following points : 



(1) The anthocodial spicules are arranged in 8 rows of 5-7 con- 



verging pairs ; they converge but slightly and are more or 

 less longitudinal in S. hartmeyeri. Moreover, the uppermost 

 spicules of the double rows do not project beyond the antho- 

 codia as they do in S. hartmeyeri. 



(2) The tip of the main " Stiitzbiindel " spicule is Smooth, v\hile in 



S. hartmeyeri the same spicule is most spinose towards the 

 free tip. 



(3) They diii'er in the dimensions and direction of the spicules in 



the cortex of the main branches. In S. hartmeyeri the cortex 

 is densely filled with large, very thick, finely spinose spindles 

 up to .5 X 0-5 mm. They seem from the drawing to be longi- 

 tudinally arranged. In the specimens in this collection the 

 spindles are for the most part arranged transversely to the 

 long axis of the branches. 

 The following measurements of these spindles were taken in 

 length and breadth in millimetres : 2 x 0-12 ; 1-8 x 0-1 : 

 0-65 X 005. 



II. The specimens differ superficially from S. mayi : 



(1) in the absence of the rigidity and brittleness characteristic of a 

 species developed in one plane. The colonies in this collection 

 have a well-developed bare trunk up to 7o cm. in length. 

 In one specimen the stem divides somewhat dicliotomously 

 into two main divisions ; in another specimen, four main 

 l)ranches take origin abruptly. From the main branches 

 secondary branches arise in every plane. 



(2) The branching is more profuse and the clusters of polyps are 



much denser than in S. mayi. 



(3) The colour-scheme is golden yellow in S. mayi. 

 They differ more intimately from S. mayi : 



(1) in the absence of a greatly developed projecting spicule at the 

 end of each double row of spicules on the anthocodiije ; 

 [60] 



